Question: $ { \left[\begin{array}{rrr}{0} & {-1} & {2} \\ {0} & {2} & {-1}\end{array}\right]+\left[\begin{array}{rrr}{-2} & {2} & {-1} \\ {-2} & {2} & {1}\end{array}\right] = {?} } $
Solution: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{0}+{-2} & {-1}+{2} & {2}+{-1} \\ {0}+{-2} & {2}+{2} & {-1}+{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-2} & {1} & {1} \\ {-2} & {4} & {0}\end{array}\right]}$